Friction-induced work hardening of cobalt-base hardfacing deposits for hot forging tools

Cobalt-base materials are widely used as weld hardfacing deposits in hot forging industry. When the cobalt-base hardfacing alloys are deposited using the MIG welding process, the weld energy with the sequences of the welding are at least the two important variables which influence the behaviour of most hardfacing deposits in service conditions. The purpose of this work is to consider their role in connection with the work-hardening ability of Stellite 21 weld hardfacing deposits. An experimental parametric study of several welded-layers related to their friction behaviour is performed. The friction-induced work hardening (FIWH) ability of Stellite 21 deposits is considered to assess the influence of the two welding parameters. Results show that depending on the used welding sequences, the amount of the applied energy determines the dilution rates across the thickness of the deposits. Microscopic observations at the friction surface confirm that the highest FIWH rates, owing to stacking faults brought out, increase the wear resistance.